One-piece component and method for its production

ABSTRACT

A one-piece component includes a first subregion made of a base material, and a second subregion made of the base material as binder with intercalated hard material particles, the second subregion being injection-molded onto the first subregion by means of MIM injection molding, so that an integral connection is formed between the first subregion and the second subregion. Furthermore, a method for producing the one-piece component by means of MIM injection molding is described.

CROSS-REFERENCE TO RELATED APPLICATION

The present application is a divisional application of U.S. patentapplication Ser. No. 13/760,181, filed on Feb. 6, 2013, which claimspriority to and the benefit of German Patent Application No. 10 2012 201880.8, filed on Feb. 9, 2012, the disclosures of which are incorporatedherein by reference.

FIELD OF INVENTION

The present invention relates to a one-piece component which has a firstand a second subregion, and to a method for producing the one-piececomponent by means of a MIM (Metal Injection Molding) method.

BACKGROUND INFORMATION

Many components which are moving or which serve as stops are subjectedto wear. Therefore there is a need to provide components that have themost advantageous wear characteristics possible. In addition, greaterwear occurs if sufficient lubrication in the case of moved components,or sufficient damping in the case of stops is impossible. One pertinentexample are devices for injecting fuel, in particular gasoline, sincegasoline exhibits very poor lubricating properties. To provide thehighest possible service life for gasoline injectors, for example,highly wear-resistant materials are used as a rule, which have theparticular disadvantage of being very costly. As an alternative, it isalso possible to use supplementary components, such as wear-resistantbushings or the like; however, this increases the number of parts aswell as the production and installation costs. In this regard,cost-effective alternatives would thus be desirable, which could solvethe wear problems without additional individual components and/oradditional working steps.

SUMMARY

By contrast, the one-piece component according to the present inventionhas the advantage that it may be produced in an especially simple aswell as cost-effective manner within the shortest period of time.According to the present invention, this is achieved by producing theone-piece component with a first subregion made of a base material, anda second subregion made of the base material as binder, together withintercalated hard material particles, utilizing MIM technology. In theprocess, the second subregion is injected onto the first subregion inorder to produce an integral connection between the two subregions. As aresult, the first and second subregions are able to be produced byinjection molding in an injection molding die.

The base material preferably is an austenitic or ferritic steel,especially steel including Fe and Cr. The hard material particlespreferably are oxides, especially Al₂O₃, ZrO₂ and/or Y₂O₃. As analternative, the hard material particles are carbides, in particulartitanium carbide, wolfram carbide, niobium carbide or tantalum carbide.As a further alternative, the hard material particles are nitrides,especially titanium nitride. With regard to the mentioned hard materialparticles, it should be noted that they are able to be mixed exclusivelywith the base material so as to form the material for the secondsubregion, or they may be mixed in any desired combinations so as toform an injectable metal powder.

Preferably, a volumetric component of the hard material particles in thematerial for the second subregion lies in a range of 5 vol. % to 20 vol.%, and especially preferably, amounts to 10 vol. %.

Preferably, the one-piece component is a component of a motor vehicle,in particular, an internal combustion engine. Especially preferably, theone-piece component is a piston, a cylinder or a valve member,especially a valve seat, a valve stop or a needle stop. Preferably, theone-piece component is a part of gasoline injectors or fuel pumps.

In addition, the present invention relates to a method for producing aone-piece component by means of 2-component MIM technology. The methodaccording to the present invention includes the steps ofinjection-molding a first subregion of the one-piece component using abase material, and injection-molding a second subregion onto the firstsubregion, the base material being used as binder and includingintercalated hard material particles as material for the secondsubregion. This makes it possible for the MIM injection-moldingtechnology to produce a one-piece component featuring an integralconnection between the first and second subregions of the component.

The one-piece component according to the present invention preferably isused in applications in which the one-piece component is moving or usedas a stop. For example, the use in piston pumps, splitter valves,injectors, and other mechanical valves may be possible. Anotherpreferred possibility is the use in fuel-carrying components, especiallyfuels having poor lubrication properties, e.g., components for gasolineengines. In this case the use as injection valve, metering valve,quantity-control valve or fuel pumps, in particular, is conceivable.

Exemplary embodiments of the present invention are described in detailbelow, with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 a schematic sectional view of a one-piece component according toa first exemplary embodiment of the present invention.

FIG. 2 a schematic sectional view of a one-piece component according toa second exemplary embodiment of the present invention.

FIG. 3 a schematic sectional view of a one-piece component according toa third exemplary embodiment of the present invention.

FIG. 4 a schematic sectional view of a one-piece component according toa fourth exemplary embodiment of the present invention.

FIG. 5 a schematic sectional view of a one-piece component according toa fifth exemplary embodiment of the present invention.

FIG. 6 a schematic sectional view of a one-piece component according toa sixth exemplary embodiment of the present invention.

DETAILED DESCRIPTION

In the following text, a one-piece component 1 according to a firstexemplary embodiment of the present invention is described in detailwith reference to FIG. 1.

One-piece component 1 encompasses a first subregion 2 made of a basematerial, and a second subregion 3 made of a material that includes thebase material as binder as well as intercalated hard material particles.An integral connection between first subregion 2 and second subregion 3is formed in the process. One-piece component 1 is produced by means of2-component MIM injection-molding, in which first subregion 2 isproduced first, in a first step, and second subregion 3 isinjection-molded onto first subregion 2 in a second step.

The use of MIM technology allows metal powders to be injection-molded,for which purpose an austenitic or ferritic steel is preferably used asbase material, and for which the relatively cost-effective base materialmay be used as binder with additional intercalated hard materialparticles for the material of second subregion 3. This makes it possibleto use a cost-effective binder for the hard material particles, which,for instance, are suitable oxides, carbides or nitrides.

The one-piece component shown in FIG. 1 is a piston for a piston machineand includes the wear-resistant layer on an outer surface of the piston.Since second subregion 3 forms the outer layer, high robustness withregard to frictional wear is obtained, and thus a long service life. Inaddition, reduced friction also leads to lower heat generation with itsattendant advantages.

As an alternative, exemplary one-piece component of the presentinvention, FIG. 2 shows a cylinder where second subregion 3 forms thebearing surface of the cylinder.

FIGS. 3 through 5 show alternative exemplary embodiments of the presentinvention, which may be used as injectors or switching valves. Secondsubregion 3 forms a valve seat in each case: for a ball valve in FIG. 3,for a cone valve in FIG. 4, and for a flat-seat valve in FIG. 5. In theexemplary embodiment shown in FIG. 5, not only is the valve seatimplemented as one-piece component having first and second subregions 2,3, but valve-closure member 6 as well, which has a first subregion 7 anda second subregion 8 as valve-closure surface. The double arrows inFIGS. 3 through 5 indicate the movement direction of the valve members.However, it would also be conceivable, for example, to implementflat-seat valve as slide valve.

FIG. 6 shows a further exemplary embodiment of the present invention ina one-piece stop 10, which features a first subregion 11 and a second,harder subregion 12. Stop 10 delimits a movement of valve member 13 inthe direction of arrow A. Via second subregion 12, stop 10 strikes acounter stop 14, which likewise may possibly be made up of a first andsecond subregion according to the present invention.

As a result, the present invention makes it possible to provide aone-piece component, which is able to be produced in cost-effectivemanner using a 2-component MIM injection-molding method. For gasolineapplications, austenitic or ferritic steel based on iron and chromiumwith a weight proportion of 13% chromium is preferably used as basematerial for all exemplary embodiments described.

What is claimed is:
 1. A method for producing a one-piece component by means of MIM injection molding, comprising: injection-molding a first subregion made of a base material, and injection-molding a second subregion made of the base material as binder and including intercalated hard material particles, onto the first subregion, such that an integral connection is formed between the first and second subregions.
 2. The method according to claim 2, wherein the base material is an austenitic or ferritic steel, which includes iron and chromium.
 3. The method according to claim 2, wherein the hard material particles are oxides, including Al₂O₃, ZrO₂ or Y₂O₃.
 4. The method according to claim 2, wherein the hard material particles are one of a) carbides, including titanium carbide, wolfram carbide, niobium carbide or tantalum carbide, or b) nitrides, including titanium nitride. 